feat(DataStore): Start/Stop implementation, 2nd approach

Amplify/Categories/DataStore/DataStoreCategory+Behavior.swift

@@ -38,6 +38,14 @@ extension DataStoreCategory: DataStoreBaseBehavior {
         plugin.delete(modelType, withId: id, completion: completion)
     }
 
+    public func start(completion: @escaping DataStoreCallback<Void>) {
+        plugin.start(completion: completion)
+    }
+
+    public func stop(completion: @escaping DataStoreCallback<Void>) {
+        plugin.stop(completion: completion)
+    }
+
     public func clear(completion: @escaping DataStoreCallback<Void>) {
         plugin.clear(completion: completion)
     }

Amplify/Categories/DataStore/DataStoreCategoryBehavior.swift

@@ -33,7 +33,29 @@ public protocol DataStoreBaseBehavior {
     func delete<M: Model>(_ modelType: M.Type,
                           withId id: String,
                           completion: @escaping DataStoreCallback<Void>)
+    /**
+     Synchronization starts automatically whenever you run any DataStore operation (query(), save(), delete())
+     however, you can explicitly begin the process with DatasStore.start()
 
+     - parameter completion: callback to be invoked on success or failure
+     */
+    func start(completion: @escaping DataStoreCallback<Void>)
+
+    /**
+     To stop the DataStore sync process, you can use DataStore.stop(). This ensures the real time subscription
+     connection is closed when your app is no longer interested in updates, such as when you application is closed.
+     This can also be used to modify DataStore sync expressions at runtime by calling stop(), then start()
+     to force your sync expressions to be re-evaluated.
+
+     - parameter completion: callback to be invoked on success or failure
+     */
+    func stop(completion: @escaping DataStoreCallback<Void>)
+
+    /**
+     To clear local data from DataStore, use the clear method.
+
+     - parameter completion: callback to be invoked on success or failure
+     */
     func clear(completion: @escaping DataStoreCallback<Void>)
 }
 

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/AWSDataStorePlugin+DataStoreBaseBehavior.swift

@@ -169,11 +169,36 @@ extension AWSDataStorePlugin: DataStoreBaseBehavior {
                              completion: onCompletion)
     }
 
+    public func start(completion: @escaping DataStoreCallback<Void>) {
+        reinitStorageEngineIfNeeded(completion: completion)
+    }
+
+    public func stop(completion: @escaping DataStoreCallback<Void>) {
+        storageEngineInitSemaphore.wait()
+        if storageEngine == nil {
+            storageEngineInitSemaphore.signal()
+            completion(.successfulVoid)
+            return
+        }
+        storageEngineInitSemaphore.signal()
+        storageEngine.stopSync { result in
+            self.storageEngine = nil
+            if #available(iOS 13.0, *) {
+                self.dataStorePublisher?.sendFinished()
+            }
+            self.dataStorePublisher = nil
+            completion(result)
+        }
+    }
+
     public func clear(completion: @escaping DataStoreCallback<Void>) {
+        storageEngineInitSemaphore.wait()
         if storageEngine == nil {
+            storageEngineInitSemaphore.signal()
             completion(.successfulVoid)
             return
         }
+        storageEngineInitSemaphore.signal()
         storageEngine.clear { result in
             self.storageEngine = nil
             if #available(iOS 13.0, *) {

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/AWSDataStorePlugin.swift

@@ -27,8 +27,9 @@ final public class AWSDataStorePlugin: DataStoreCategoryPlugin {
 
     let validAuthPluginKey: String
 
-    /// The local storage provider. Resolved during configuration phase
     var storageEngine: StorageEngineBehavior!
+    var storageEngineInitSemaphore: DispatchSemaphore
+    var storageEngineBehaviorFactory: StorageEngineBehaviorFactory
 
     var iStorageEngineSink: Any?
     @available(iOS 13.0, *)
@@ -52,28 +53,32 @@ final public class AWSDataStorePlugin: DataStoreCategoryPlugin {
         self.isSyncEnabled = false
         self.validAPIPluginKey =  "awsAPIPlugin"
         self.validAuthPluginKey = "awsCognitoAuthPlugin"
-
+        self.storageEngineBehaviorFactory =
+            StorageEngine.init(isSyncEnabled:dataStoreConfiguration:validAPIPluginKey:validAuthPluginKey:modelRegistryVersion:userDefault:)
         if #available(iOS 13.0, *) {
             self.dataStorePublisher = DataStorePublisher()
         } else {
             self.dataStorePublisher = nil
         }
+        self.storageEngineInitSemaphore = DispatchSemaphore(value: 1)
     }
 
     /// Internal initializer for testing
     init(modelRegistration: AmplifyModelRegistration,
          configuration dataStoreConfiguration: DataStoreConfiguration = .default,
-         storageEngine: StorageEngineBehavior,
+         storageEngineBehaviorFactory: StorageEngineBehaviorFactory? = nil,
          dataStorePublisher: ModelSubcriptionBehavior,
          validAPIPluginKey: String,
          validAuthPluginKey: String) {
         self.modelRegistration = modelRegistration
         self.dataStoreConfiguration = dataStoreConfiguration
         self.isSyncEnabled = false
-        self.storageEngine = storageEngine
+        self.storageEngineBehaviorFactory = storageEngineBehaviorFactory ??
+            StorageEngine.init(isSyncEnabled:dataStoreConfiguration:validAPIPluginKey:validAuthPluginKey:modelRegistryVersion:userDefault:)
         self.dataStorePublisher = dataStorePublisher
         self.validAPIPluginKey = validAPIPluginKey
         self.validAuthPluginKey = validAuthPluginKey
+        self.storageEngineInitSemaphore = DispatchSemaphore(value: 1)
     }
 
     /// By the time this method gets called, DataStore will already have invoked
@@ -82,33 +87,28 @@ final public class AWSDataStorePlugin: DataStoreCategoryPlugin {
     public func configure(using amplifyConfiguration: Any?) throws {
         modelRegistration.registerModels(registry: ModelRegistry.self)
         resolveSyncEnabled()
-
-        try resolveStorageEngine(dataStoreConfiguration: dataStoreConfiguration)
-
-        try storageEngine.setUp(modelSchemas: ModelRegistry.modelSchemas)
-
-        let filter = HubFilters.forEventName(HubPayload.EventName.Amplify.configured)
-        var token: UnsubscribeToken?
-        token = Amplify.Hub.listen(to: .dataStore, isIncluded: filter) { _ in
-            self.storageEngine.startSync()
-            if let token = token {
-                Amplify.Hub.removeListener(token)
-            }
-        }
     }
 
-    func reinitStorageEngineIfNeeded() {
+    func reinitStorageEngineIfNeeded(completion: @escaping DataStoreCallback<Void> = {_ in}) {
+        storageEngineInitSemaphore.wait()
         if storageEngine != nil {
+            storageEngineInitSemaphore.signal()
+            completion(.successfulVoid)
             return
         }
         do {
             if #available(iOS 13.0, *) {
-                self.dataStorePublisher = DataStorePublisher()
+                if self.dataStorePublisher == nil {
+                    self.dataStorePublisher = DataStorePublisher()
+                }
             }
             try resolveStorageEngine(dataStoreConfiguration: dataStoreConfiguration)
             try storageEngine.setUp(modelSchemas: ModelRegistry.modelSchemas)
-            storageEngine.startSync()
+            storageEngineInitSemaphore.signal()
+            storageEngine.startSync(completion: completion)
         } catch {
+            storageEngineInitSemaphore.signal()
+            completion(.failure(causedBy: error))
             log.error(error: error)
         }
     }
@@ -118,11 +118,13 @@ final public class AWSDataStorePlugin: DataStoreCategoryPlugin {
             return
         }
 
-        storageEngine = try StorageEngine(isSyncEnabled: isSyncEnabled,
-                                          dataStoreConfiguration: dataStoreConfiguration,
-                                          validAPIPluginKey: validAPIPluginKey,
-                                          validAuthPluginKey: validAuthPluginKey,
-                                          modelRegistryVersion: modelRegistration.version)
+        storageEngine = try storageEngineBehaviorFactory(isSyncEnabled,
+                                                         dataStoreConfiguration,
+                                                         validAPIPluginKey,
+                                                         validAuthPluginKey,
+                                                         modelRegistration.version,
+                                                         UserDefaults.standard)
+
         if #available(iOS 13.0, *) {
             setupStorageSink()
         }
@@ -184,4 +186,3 @@ final public class AWSDataStorePlugin: DataStoreCategoryPlugin {
     }
 
 }
-

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Storage/StorageEngine+SyncRequirement.swift

@@ -12,25 +12,30 @@ import AWSPluginsCore
 
 extension StorageEngine {
 
-    func startSync() {
+    func startSync(completion: @escaping DataStoreCallback<Void>) {
         guard let api = tryGetAPIPlugin() else {
             log.info("Unable to find suitable API plugin for syncEngine. syncEngine will not be started")
+            completion(.failure(.configuration("Unable to find suitable API plugin for syncEngine. syncEngine will not be started",
+                                               "Ensure the API category has been setup and configured for your project", nil)))
             return
         }
 
         let authPluginRequired = requiresAuthPlugin(api: api)
 
         guard authPluginRequired else {
             syncEngine?.start(api: api, auth: nil)
+            completion(.successfulVoid)
             return
         }
 
         guard let auth = tryGetAuthPlugin() else {
             log.warn("Unable to find suitable Auth plugin for syncEngine. Models require auth")
+            completion(.failure(.configuration("Unable to find suitable Auth plugin for syncEngine. Models require auth",
+                                               "Ensure the Auth category has been setup and configured for your project", nil)))
             return
         }
-
         syncEngine?.start(api: api, auth: auth)
+        completion(.successfulVoid)
     }
 
     private func tryGetAPIPlugin() -> APICategoryGraphQLBehavior? {

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Storage/StorageEngine.swift

@@ -10,6 +10,14 @@ import Combine
 import Foundation
 import AWSPluginsCore
 
+typealias StorageEngineBehaviorFactory =
+    (Bool,
+    DataStoreConfiguration,
+    String,
+    String,
+    String,
+    UserDefaults) throws -> StorageEngineBehavior
+
 // swiftlint:disable type_body_length
 final class StorageEngine: StorageEngineBehavior {
 
@@ -386,6 +394,16 @@ final class StorageEngine: StorageEngineBehavior {
         }
     }
 
+    func stopSync(completion: @escaping DataStoreCallback<Void>) {
+        if let syncEngine = syncEngine {
+            syncEngine.stop { _ in
+                completion(.successfulVoid)
+            }
+        } else {
+            completion(.successfulVoid)
+        }
+    }
+
     func reset(onComplete: () -> Void) {
         // TOOD: Perform cleanup on StorageAdapter, including releasing its `Connection` if needed
         let group = DispatchGroup()

AmplifyPlugins/DataStore/AWSDataStoreCategoryPlugin/Storage/StorageEngineBehavior.swift

@@ -20,7 +20,7 @@ protocol StorageEngineBehavior: class, ModelStorageBehavior {
     var publisher: AnyPublisher<StorageEngineEvent, DataStoreError> { get }
 
     /// start remote sync, based on if sync is enabled and/or authentication is required
-    func startSync()
-
+    func startSync(completion: @escaping DataStoreCallback<Void>)
+    func stopSync(completion: @escaping DataStoreCallback<Void>)
     func clear(completion: @escaping DataStoreCallback<Void>)
 }